A Minnesotan traveler contracted measles from a toddler he had never met, by passing through the same airport gate as the child.
In case that highlights the ease at which the virus can spread, the Center for Disease Control said it was alerted to the case by the Minnesota Department of Health in April 2014.
It comes after a child aged 19 months developed a rash on April 17, while on an international flight from India to Minneapolis, via a connecting flight from Chicago.
Health officials investigated whether any of the passengers on either flights were infected – with measles infectious four days before and after a rash appears – but didn't find any cases.
However, on May 5, the Massachusetts Department of Public Health contacted Minnesota to report that a 46-year-old Minnesotan man was traveling in the east coast state for business when he came down with a measles rash.
He had no known exposures or international travel, nor was he on the same flight as the infected child. However, it emerged that he had passed through the Chicago airport and used the same gate for his flight as the girl had.
It is believed that the man became infected in a period when the man arrived from his flight at the gate, where the child was waiting to depart with her family on their flight to Minneapolis.
"Measles is a highly communicable disease, and infectious droplets can remain suspended in the air for up to two hours after an infected person leaves the area," the CDC report says.
The 46-year-old was kept in isolation at a Massachusetts hospital for the last five days of his infectious period, while the child spent three days in the hospital in Minnesota. Both made full recoveries.
According to NBC News, the child had received one measles vaccine but not the second dose (5 percent of children need two doses before they're fully protected) while the man could not remember ever being vaccinated.
Measles: The highly contagious virus
The CDC says that measles symptoms generally appeared 7-14 days after infection, and begin with high fever, a cough, a runny nose and red, watery eyes, before a rash breaks out.
It is considered one of the most contagious known human viruses – and if one person has it, 90 percent of people close to that person will also become infected if they're not immune.
The Mayo Clinic reports that measles can lead to complications, such as bronchitis or pneumonia.